The present invention is directed to a dental handpiece which contains a coupling member in which a duct for delivery of a coolant to a discharge nozzle at the head end of the handpiece is arranged, the handpiece includes a check valve that will close or release the duct dependent on the fluid pressure in the duct.
European Patent 0 271 597 discloses a handpiece which has a check valve. The check valve serves the purpose of preventing the liquid from flowing back into the delivery paths after the liquid is shut off and thereby prevents bacteria picked up from the treatment region or oral cavity from proceeding into the apparatus region, which cannot be sterilized after a treatment. In this known handpiece, the check valve is arranged in the region of the head housing of the handpiece. In order to remove the valve member from the duct, a screw cover on the head housing must be removed and then the drive unit arranged in the head housing must also be removed to provide space for removing the valve member.
As already addressed at the onset, the valve serves the purpose of preventing a return flow of the liquid charged with bacteria after the flow of liquid has been shut off externally from the handpiece. The intentional back-absorption or suction for avoiding the formation of droplets at the exit location of the nozzle is not achieved with this type of valve structure.